One of the requirements for the AmavisD service to start is that the hostname is a FQDN (Fully Qualified Domain Name).
During the installation, you can put in a non-fully qualified name (e.g., SpamTitan), but if you do that, the AmavisD service (Reporting > System Information > Services) will no start.
* Keep in mind, the test messages out of the appliance (i.e., The Forgot Password and Domain Test emails) will still go out because they don't depend on Amavisd, but inbound mail will not be processed.
To fix, simply do the following:
- Go to System Setup > Mail Relay > General Settings, and set the Hostname to a FQDN (example: spamtitan.domain.com -- you do not need to included the final "." like you do for DNS records.) and Save
- Change the Banner Response to match
- Go to Reporting > System Information > Services, and: Stop Postfix, Start Amavisd, Start Postfix, the wait about 30 seconds
- Go to Reporting > System Information > Tools (scroll down then page), then Flush Mail Queue, by clicking the Flush button (this will force redelivery of all deferred messages)